?03 Chevy Impala 3.4l 100k Gulping/Jolting

?03 Chevy Impala 3.4l 100k Gulping/Jolting.

My father?s car. He?s in the process of pulling the OBD-II codes ? if there are any.

Here?s a summary of what he described to me:

Car has been having problems with ?gulping jolts? on and off, almost resulting in a stall. Mechanic took a look at it and ended up installing a ?transmission kit? and fluid for $125+ (said an indicator light told him the fluid was low ? is there such an indicator for transmission fluid on this car??). Of course, this did not fix the problem. Problems seems to happen from speeds up to 45 mph (and lower speeds may be worse). Car seems to perform OK at Interstate speeds (65 mph+), but there is a rough feeling underfoot. Problem does not start right away ? maybe 5-10 miles after startup. Feels like it?s not getting enough gas.

His intake gaskets were supposedly replaced about a year or so ago.

why were the intake gaskets replaced? Is the intake manifold warped? is there a loose or cracked vacume hose associated with the intake manifold, (this will be indicated by a whistling noise if you let the engine idle with the hood up. And it should also have a very rough idle if there is a vacume leak around the intake gasket.) Do the jolts occur when the transmission is shifting from lower gear to higher gear? Does this transmission have a vacume valve on it?

The intake gaskets were replaced presumably because they were leaking. I had to do the same job on my '02 Impala (also 3.4l). With my Impala, I had fudgicle sludge under the radiator cap, and I think at one point I verified my father’s Impala had the same problem. This was/is a well-known and widespread problem across engines of multiple GM models.

My father has not reported that the car has a rough idle - only that it “gulps” and “jolts” sometimes after driving a few miles at speeds up to about 45 mph. This problem does not happen all the time, so I’m thinking it’s not transmission-related.

I don’t know if there is a vacuum valve on the transmission, but I will find out.

gunky sludge under the radiator cap does not sound like it is directly related to the intake maniflod gasket, but could be related to the head gasket. I dont know what a gulping jolt is exactly, though it is a colorful description. The thing is if the transmission is having a hard time shifting, it will kind of thunk and jump when shifting, and this happens between zero and about 45, because after that it is in high gear, and so it wont happen again at freeway speed. by your answer to the whistling noise and rough idle question, you tend to rule out a vacume leak, or a leaking intake gasket problem.

The transmission is a 4t65e with no vacuum modulator on it.

As for the problem, I find it impossible to even start thinking about the “gulping jolts.” ask your dad to try to give a better description of what the car is doing.

What led the mechanic to a shift kit and what was the nature of said kit?

First of all, my Dad has told me the CHECK ENGINE LIGHT is not on, so there are no codes to read.

Secondly, the LOW FLUID issue was with the BRAKE FLUID, not the tranny fluid. The tranny fluid was apparently changed for another reason (maybe routine maintenance). My guess is this “kit” was a new pan gasket and filter.

I’ll try to get a better description from him. Unfortunately, the car is not near me and I cannot drive it myself to provide the better description.

There are codes that can be present even without the check engine light. These require more sophisticated scanners than the typical OBD II code readers. So if there is reason to believe that there is a transmission problem (that mechanic apparently thought so) it may need to be scanned by a transmission shop with the right equipment.

I’ll be able to drive the car myself shortly - then I’ll post back.

What about laptop software to capture real-time diagnostic data? Any recommendations there?

There are 99 transmission related TSB’s for your car (sounds like a real winner) many of them use the words “shudder/chuggle” you may want to take a look.